Semiconductor structure for photodetector

Abstract

A photodiode comprises e.g. an n-type semiconductor layer, a p-type semiconductor region selectively formed in a central part from a surface of the n-type semiconductor layer, a dish-like shaped pn-junction therebetween, an annular electrode formed on the p-type region, an electrode formed on the other side of the n-type semiconductor layer, and a dielectric layer deposited on the n-type semiconductor layer for preventing light from attaining to the semiconductor layer by reflecting a dielectric multilayer consisting of two different media having effective thicknesses equal to one fourth of the wavelength of the light.

What we claim is: 
     
       1. A photodetector comprising: a semiconductor layer being one of an n-type and a p-type having two surfaces,   a semiconductor region being one of a p-type and an n-type, respectively, selectively formed in a central part from one surface of the semiconductor layer,   a dish-like shaped pn-junction formed between the semiconductor layer and the semiconductor region,   an annular electrode formed on the semiconductor region,   a second electrode formed on the other surface of the semiconductor layer, and   a dielectric layer formed outside of the annular electrode from preventing light from reaching the semiconductor layer by reflecting or absorbing the light.   
     
     
       2. A photodetector comprising: an semiconductor substrate being one of an n+-type and p+-type having, two surfaces,   an undoped semiconductor layer deposited on one surface of the semiconductor substrate,   a semiconductor region, being one of a p-type or n-type region respectively, selectively formed in a central part from one surface of the undoped semiconductor layer,   a dish-like shaped pn-junction formed between the undoped semiconductor layer and the semiconductor region,   an annular electrode formed on the semiconductor region,   a second electrode formed on the other surface of the semiconductor substrate, and   a dielectric layer formed outside of the annular electrode for preventing light from reaching the semiconductor layer by reflecting or absorbing the light.   
     
     
       3. A photodetector as claimed in claim 1 or 2, wherein the dielectric layer is a dielectric multilayer including alternating deposited first sublayers and second sublayers with different refractive indices having effective thickness equal to one fourth the wavelength of the light. 
     
     
       4. A photodetector as claimed in claim 1 or 2, wherein the dielectric layer is an opaque medium with an absorption factor high enough so that the light cannot reach the semiconductor under dielectric layer. 
     
     
       5. A photodetector as claimed in claim 1 or 2, wherein the dielectric layer is a dielectric multilayer including alternating deposited a-Si sublayers with a refractive index of 3.2 and SiN sublayers with a refractive index of 1.8, with the sublayers having effective thicknesses equal to one fourth of a wavelength of the light. 
     
     
       6. A photodetector as claimed in claim 1 or 2, wherein the light has a wavelength of 1.55 μm and the dielectric layer is a dielectric multilayer including alternating deposited a-Si sublayers with a refractive index of 3.2 having a thickness of 120 nm, and SiN sublayers with a refractive index of 1.8 having a thickness of 215 nm. 
     
     
       7. A photodetector comprising: an n +  -type InP substrate with two surfaces,   an undoped InP buffer layer deposited on the n +  -type InP substrate,   an undoped InGaAs receiving layer deposited on the undoped InP buffer layer,   an undoped InP window layer,   a p-type region selectively formed in a central part of the undoped InP window layer and upper half of the InGaAs receiving layer by ion-implantation or diffusion of Zn,   a dish-like shaped pn-junction formed between the p-type region and the undoped InP window layer and the undoped InGaAs receiving layer,   an annular electrode formed on the p-type region,   another electrode formed on the other surface of the n +  -type InP substrate,   an antireflection film deposited on the p-type region (3) enclosed by the annular electrode,   a protective film deposited on the undoped InP window layer outside of the annular electrode, and   a dielectric layer formed on the protective film for preventing light from reaching the undoped InGaAs receiving layer by reflecting or absorbing the light completely.   
     
     
       8. A photodetector as claimed in claim 7, wherein the dielectric layer is a dielectric multilayer fabricated by depositing by turns a-Si sublayers with a refractive index of 3.2 having a thickness of 120 nm, and SiN sublayers with a refractive index of 1.8 having a thickness of 215 nm.